The invention relates to a device for the distraction of bone segments, particularly in the jaw region, according to the preamble of claim 1.
Such a device is known, for example, from the International Patent WO 94/22400. This device has two components whose mutual spacing is variable and which are positioned relative to one another by means of guide rods. A threaded spindle, arranged between the guide rods, is provided for varying the spacing. At right angles to the threaded spindle, a drive shaft is connected via a bevel gear to a threaded spindle in order to variably set the distance of the two components relative to each other. In order to fasten the two components to the bone segments, they respectively have several perforated plates arranged in a plane, in order to fasten the components to the bone segments by means of fixing pins or screws.
Such devices have a considerable structural size. In addition, such devices are principally suitable for use in the skull or face region. A use in the jaw region can admittedly be provided in the lateral lower jaw, but fitting is problematic because of the structural size, and accessibility is greatly impeded. For example, a nerve whose position is difficult to identify runs in the lateral region of the jaw, so that there is a very great danger of damage, particularly with such devices. In the lower jaw, this can lead to a numb lower lip. In the anterior jaw, accessibility to external devices is limited by important muscle structures.
For the reconstruction of, for example, vertical bone deficits, the use of such devices, or of devices used with such a device, is only possible with considerable tissue traumatization. Such reconstructions are required because the lack of functional loading of force application leads to atrophy of the alveolar process in the upper and lower jaw due to inactivity, and this therefore recedes.
For the reconstruction of larger vertical bone deficits, for example, of the alveolar process in the upper and lower jaw, the augmentation takes place at that time with a free bone transplant, which is usually removed as a pelvic chip in order to implant this into the jaw bone. The soft tissues are then mobilized, drawn over the bone transplant, and sewn. In this technique for vertical bone augmentation, a soft tissue correction usually has to be undertaken for the restoration of the buccal cavity. This procedure has the disadvantage that several operations are necessary; the patient has on the one hand to undergo a surgical operation, and moreover is burdened with a removal morbidity. Furthermore, the patient cannot regain his employed life for a longer time. Since the retrogression of the bone after tooth extraction mostly occurs in patients of advanced age, further dangers, such as for example thromboses, embolisms, hemorrhage or the like, have to be taken into account in connection with the above-described reconstruction of large bone deficits.
Reconstruction by implants is necessary for the production and maintenance of a denture foundation in order to fully restore the function of mastication.
The invention therefore has as its object to provide a device with which removal morbidity is avoided, building up of bone is attained in a shorter time, and a simple positioning of the device, and also its removal without problems after the bone deficit has been built up, are made possible. Furthermore, this device is to act mechanically as close as possible to the location of the distraction, and is to make possible, after removal, a simple introduction of the implant.
This object is attained according to the invention by the device according to claim 1.
The arrangement within the bone to be built up makes it possible for the mechanical action to take place at the exact place at which bone formation takes place by the very vigorous healing tissue, the so-called callus. In particular, in use for reconstruction of the jaw ridge in the upper and lower jaw by vertical callus distraction, a fine bone cut can be sawn in a jaw which is too flat, so that the portion previously bearing teeth can be moved a little. The device according to the invention is preferably provided at this place of the future artificial tooth root or of the implant, and the bone segment can be raised up with it in a controlled manner so that callus tissue forms and can lead to the reconstruction of the bone. Muscle forces which come into play can easily be compensated by this arrangement, since the mechanical action of the distraction device can be exerted directly at the place to be acted on.
Furthermore, this device has the advantage that a single tooth segment in the jaw region, that is, the denture foundation for a single tooth, can be rehabilitated. Moreover, a combination of several distraction devices can be provided, matched to the size or length of the bone segment to be distracted.
The device according to the invention has the further advantage that the soft tissues in the buccal vestibule and buccal cavity are not required in order to cover the bone implant from the pelvic region. The soft tissue correction usually necessary in the alternative procedures can thereby be omitted. The soft tissues can instead grow in parallel with the callus. Furthermore, removal morbidity, which can entail chronic pain in the pelvic region, hemorrhages, or the like, can be avoided.
An advantageous constitution of the invention provides that the maximum diameter of the outer and/or inner sleeve of the device according to the invention is of the same size as, or at least slightly smaller than, the diameter of the dental implant. As a result, the dental implant can be inserted after the removal of the distraction device, without further surgical operations being necessary. For example, the implant can then be immediately screwed in and fastened. The treatment times can thus be shortened. Moreover, an operation of this kind can be performed by dentists, without a stay in a clinic being necessary.
According to a further advantageous constitution of the invention, it is provided that a section with an external thread is provided at least partially on the inner and outer sleeves. It can thereby be made possible for the device to be inserted or screwed in a simple manner into a bore of the bone, without furthermore requiring for this purpose, fastening means which would be problematic to install particularly in the case of bone ridge widening.
According to a further advantageous constitution, it is provided that the external thread of the inner and outer sleeves is made of equal diameter. A bore in the bone section to be widened can then be established with a bone drill, in order to subsequently set the device internally of the bone, directly or indirectly.
It can furthermore be advantageously provided that the external threads of the inner and outer sleeves are formed as self-tapping threads. An insertion of the device into the bone section to be widened, directly after the bore is formed, can thereby be made possible.
So that a simple insertion and removal of the device can be made possible, it is advantageously provided that the inner and outer sleeves are guided, mutually secured against torsion. The device can thus be inserted and removed as a unit.
It is furthermore advantageously provided, for the simplification of handling, that the outer sleeve of the device has a mounting section constructed to receive a tool wrench. This mounting section can, for example, have a polygonal head, and can be, for example, a hexagonal nut or the like, so that the device can be positioned and also removed with a tool wrench.
According to a further advantageous constitution of the invention, it is provided that the mounting section of the outer sleeve is constructed as a receiving section for a dental implant. It can thereby be made possible that the distraction device no longer needs to be removed after a callus distraction, and can serve as the denture foundation. The medical operations for the construction of a dental implant can thereby be further reduced.
According to a further advantageous constitution of the invention, it is provided that the adjusting device is mechanically constructed and includes a threaded spindle which is arranged in a threaded section of the inner sleeve, and that a head of the threaded spindle is fastened axially to the external sleeve. The mechanical constitution of the distraction device makes possible a precise adjustment of the rate of distraction, which can be, for example, 0.25 mm to 0.5 mm per day. The rate of distraction can be precisely set by the number of turns, in dependence on the different constitution of the thread pitch. Furthermore, it can be advantageously attained by the securement against torsion that the rotational movement can be converted into an axial path movement or longitudinal movement.
A head of the threaded spindle is advantageously fastened in the outer sleeve, with the head situated near the mounting section of the distraction device. Good accessibility for the extension is thereby provided, since the mounting head protrudes through a soft tissue opening and accessibility can thus be given for the purpose of extension.
According to a further alternative embodiment of the invention, it is provided that the adjustment device is constituted as an osmotic pressure chamber with a semipermeable wall. It can thereby be made possible, by means of the concentration equalization of, for example, sodium chloride solutions, for the inner sleeve to be movable relative to the outer sleeve. The maximum displacement path can be determinable by means of the degree of the concentration difference.
A further alternative embodiment of the adjusting device is provided by a pressure spring mechanism which makes possible a continuously adjustable, or for example finely stepped, rate of distraction. The device can furthermore have an adjusting device which is actuatable by means of compressible materials, preferably with air-elastic or rubber-elastic materials.
Further advantageous embodiments of the invention are described in the further claims.